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View LD100's profile

Centering router's bit when router is in a lift?

by LD100
posted 01-05-2021 05:58 AM


20 replies so far

View Andybb's profile

Andybb

3279 posts in 1689 days


#1 posted 01-05-2021 08:26 AM

JMHO…

Unless it is drastically off-center I wouldn’t give it a second thought. Just make sure you use an insert wide enough for the bit you’re using. Even 3/100 of an inch seems inconsequential.

-- Andy - Seattle USA

View Rich's profile

Rich

6851 posts in 1675 days


#2 posted 01-05-2021 12:49 PM

Andy is right. It doesn’t matter.

However, without knowing what lift you have it’s impossible to advise you on moving the motor in the lift to get it centered.

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

View HokieKen's profile

HokieKen

17548 posts in 2224 days


#3 posted 01-05-2021 01:27 PM

The only time it would matter is if you have a throat insert that accepts template bushings and are using those bushings.

If that’s the case, you probably need to be able to tweek your position. But, like Rich said, we can’t really offer advice without more details.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View jbmaine's profile

jbmaine

160 posts in 556 days


#4 posted 01-05-2021 01:38 PM

I’ve had a lift for years and never gave centering the bit a thought. Then I bought a Leigh RTJ400 and found my router was out of center to the lift and had all kinds of problems trying to use the elliptic bushing. I ended up shimming the router to bring it back into concentricity. I’m a retired tool and die maker and have lots of measuring tools so this is how I checked it.

At the end of the day, unless you try to use bushings, concentricity should not matter.

View northwoodsman's profile

northwoodsman

553 posts in 4832 days


#5 posted 01-05-2021 02:02 PM

Templates used in a router table application are most often referenced off a bearing on the bit so the placement of the router in opening shouldn’t matter. I have 9 routers and you got me thinking… I don’t ever recall using a bushing set-up in my router table, nor can I think of an instance where I would. If it keeps you up at night you could always use shims to center your router in the lift. Is there any room to rotate your router in the lift? Perhaps that’s all it would take.

-- NorthWoodsMan

View splintergroup's profile

splintergroup

5140 posts in 2308 days


#6 posted 01-05-2021 02:48 PM

A year ago I revisited the router installation in my older Woodpecker PRL (looks almost exactly like jblmaine’s picture above).

I noticed that the router was not quite perfectly square to the surface so I spent some time setting it up square with the collar that secures the motor to the lift. These lifts are CNC machined and should be plenty well machined with their mechanism perfectly centered and square to the top plate. Any misalignment most probably is caused by the router not being installed correctly.

What I did different to correct my problem was to tighten the collar to my router motor until I could still just spin the motor in the collar by hand. I felt a small “thunk” and the motor loosened up a bit. I had tightened the collar while the motor was slightly cocked and the proceedure allowed it to pop into alignment. After snugging up the collar again, everything stayed true.

jb shows am excellent way to precisely measure for centering and if you let the indicator ride on the surface, it also will show you if it is all perpendicular to the surface.

If after being sure your router shaft is truly perpendicular to the table surface and these type of steps don’t fully correct any X/Y offset, you’ll need to try shimming between the motor and collar. Your 0.012” is not much and even a section of aluminum can or a few layers of paper can work in a pinch.

Also don’t be afraid to rotate the motor in the collar and try different positions. Any off center in the router motor machining can be used to compensate for any off center machining/assembly in the lift

View GR8HUNTER's profile

GR8HUNTER

8427 posts in 1798 days


#7 posted 01-05-2021 03:34 PM

DO THIS :<)))))))))))

-- Tony---- Reinholds,Pa.------ REMEMBER TO ALWAYS HAVE FUN :<))

View LD100's profile

LD100

9 posts in 201 days


#8 posted 01-05-2021 04:45 PM

Hello all. First, I want to express my thanks for all of your thoughtful responses.

I agree with much of what has been said. It doesn’t matter if the bit is offset from the insert in a router table unless bushings are involved. Bushings don’t directly attach to bits like bearings do, so in this case bit to insert coaxial alignment is important. (Hence the use of centering cones on hand held routers.)

The Leigh RTJ400 is exactly the jig I had in mind that triggered this thread. This particular jig is for router tables only, and you move the jig (and the work piece), not the router. The guide bushing is attached to the table insert and it is elliptical. Because it’s elliptical, by rotating it judiciously one can actually tune the fit of the joint (loose vs tight). However, if the bit isn’t centered on the insert, the jig won’t work as expected. All your tails will be shifted. Which direction and how much they are shifted depends on the offset error in your particular router table.

For those interested here is an old video discussing this jig. (in the video, it’s mentioned that the jig includes a DVD! What’s that?)

When installing my Porter Cable router into my table, I observed that when I rotated the router body, or even simply removed it and put it back in, a slightly different offset error would result. I found this a bit maddening because it was seemingly random. Your tips and comments are all helpful here and dead on.

If I can get my router centered to my satisfaction and lock it in place, I will be happy leaving the Porter Cable permanently in place and call it good.

I purposely did not mention my particular equipment because I was looking for general information. I did not want to start a discussion about “this brand vs that brand” since my purchase is a done deal for now. My lift is a SawStop lift, and I chose this lift because I like the design of the lift mechanism and it’s preconfigured for my saw. The clamp mechanism on it is simple, which I like, but the alignment between this clamp mechanism and the table seems entirely dependent upon SawStop’s component accuracy or perhaps a factory alignment step. There is no mention of a way to adjust the clamp position. I have reached out to SawStop to inquire but no answer yet.

The router clamp has a 4.2 inch diameter. It is aluminum and is held in position by three fasteners (see arrows). I don’t know if the fasteners are locating (e.g. precision shoulder screws) or if the clamp is simply jig-located in the factory and the fasteners locked down.

SawStop includes collars for 3.25 inch and 3.50 inch diameter routers. The manual is vague in my opinion, saying that “if your router is significantly smaller, use a collar.” The clamp is not designed for routers larger than 4.2 inches, and the manual fails to mention that if your router isn’t exactly either 3.25” or 3.50” their included collars are not going to work. The aluminum clamp flexes when tightened but it is not designed to flex much. With the provided sizes they are covering “most routers” out in the world, although I have read complaints about router compatibility with this lift and SawStop’s failure to make this crystal clear up front to shoppers.

One thought I had was that I could loosen the three bolts, reposition the clamp, and re-tighten. I would not do this without express guidance from SawStop. (I don’t want to lose a factory alignment and then create a nightmare for myself.)

My background is mechanical engineering and I regularly work closely with tool and die makers. Thanks again for all of your advice.

View Andybb's profile

Andybb

3279 posts in 1689 days


#9 posted 01-05-2021 04:52 PM



DO THIS :<)))))))))))

- GR8HUNTER

PERFECT! :-)

-- Andy - Seattle USA

View splintergroup's profile

splintergroup

5140 posts in 2308 days


#10 posted 01-05-2021 05:22 PM

Another simple technique that I used before resorting to the dial gauges is to select a guide bushing with either a 1/2” ID (best) or a 1/4” ID if you don’t have a 1/2”.

Hopefully the bushing has a good fit into your insert for a permanent fix, but some slop can be useful.

Assuming you have your router mounted as vertical as possible, chuck up a 1/2” drill bit or other precision 1/2” rod.

With the bushing installed, you should be able to “coax” the router enough to allow the shaft to slip in/out of the bushing as it is raised/lowered.

If your bushing has some slop in the insert, you can raise the router and slide the bushing retaining nut over the shaft and let it slide down to the router. With the shaft raised above the table surface, slide the bushing over the shaft and into the insert.

If you have enough hand room underneath, you might be able to spin the nut onto the bushing and snug it up a bit, effectively centering it. Lower the router so the shaft is out of the bushing, carefully remove the insert and tighten up the bushing.

Reinstall the insert/bushing with the same indexing and you should be near dead centered.
This worked well for me, but with a different lift there may be issues that make it un-doable 8^)

View LD100's profile

LD100

9 posts in 201 days


#11 posted 01-05-2021 05:28 PM

Thanks, splintergroup. That is exactly the process I had in mind with a variation. I was going to use a Jessum insert with a 1/2” opening.

The insert can be seen here.

View HokieKen's profile

HokieKen

17548 posts in 2224 days


#12 posted 01-05-2021 05:30 PM

If I’m understanding the clamping mechanism correctly, any deviation from the nominal diameter of 4.2” will shift the router off-center by 1/2 that amount. This is based on one side of the clamp being fixed and the other side moving when clamping. So if your router measures 4.15” diameter instead of 4.2”, you’re spindle will be off-center by .025”.

If that is the case, I don’t really see any option other than to adjust the position of the clamp for the router being used. I’ll be curious what SS has to say about it. As far as loosing the factory alignment… it doesn’t sound to me like you can make it any worse.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View LD100's profile

LD100

9 posts in 201 days


#13 posted 01-05-2021 06:22 PM

HokieKen, you are exactly right.

The two supplied plastic router collars (3.25” & 3.50” ID) have a 4.2” OD. However these collars are split collars which allows them to snug down on your particular router. Therefore the OD of the collar can deviate a bit depending on your exact router OD.

Looking at the clamp, the “theoretical center” of the clamp is fixed in place with some location tolerance (whatever it is). In addition, if your collar+router OD is not exactly 4.20” your router center will shift off center, adding to any offset error. The clamp is clean and simple, but has issues. It is what it is, I guess. I haven’t explored JessEm’s lift in detail, but the JessEm clamp seems to have 4 clamp elements coming in from four corners. This would suggest it’s more accurate for centering than SawStop’s clamp, but maybe it isn’t in actual practice. Not sure.

So far, I love the SawStop’s lift mechanism but I don’t love its clamping mechanism. I don’t hate it, but I just don’t think it’s that great. I’m suspending final judgement while hoping I will get mine centered good enough in the end and leave it in place.

I will definitely post anything I hear from SawStop.

View HokieKen's profile

HokieKen

17548 posts in 2224 days


#14 posted 01-05-2021 07:41 PM

If your router diameter (or collar diameter when clamped on the router) are smaller than 4.2”, you could use shim stock to get the router centered. If your router/collar are larger than 4.2”, that won’t work though. That of course assumes that the clamp is perfectly centered to the insert at the nominal 4.2”.

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

View LD100's profile

LD100

9 posts in 201 days


#15 posted 01-10-2021 02:15 AM

Last week has fully passed and I haven’t yet heard back from SawStop. Oh well.

I purchased a set of phenolic inserts from Lee Valley. They work with the SawStop router table. I used a 1/2 inch drill bit (which is 0.495 inch by my calipers) in my router’s collet and used the 1/2 inch phenolic insert (hole diameter was about 0.510 inch and not perfectly circular) as a guide, with the goal of my drill bit turning by hand without scraping the guide.

It took about 1.25 hours. Through both the careful application of painters tape to the body of my router, and rotating my router in the lift’s clamp, I was finally able to find the sweet spot where the bit turned freely in the insert. And, I could look down on the bit from above and see a small consistent gap between the bit and the hole. Based on the above I am probably with 0.005 inch of center.

I plan on leaving this router in place on the lift and see how it goes. Hopefully I won’t have to revisit it for a good while. Thanks for your tips.

LD

View splintergroup's profile

splintergroup

5140 posts in 2308 days


#16 posted 01-11-2021 03:56 PM

Good update LD!
Your last comment made me think.
I decided to recheck my router install for square with a high resolution dial gauge. It actually is still set up just fine.
The will power to resist leaving well-enough alone is hard for me to find. I always want to re-tweak stuff and end up spending more hours redoing what should have been left alone. 0.005 is basically invisible so you are all set.
Hopefully nothing will require you to remove the router for some time!

View EEngineer's profile

EEngineer

1137 posts in 4699 days


#17 posted 01-11-2021 09:17 PM

I disagree with those who say centering the router doesn’t matter. I have an old Woodpecker 420 Quicklift and I depend on that router bit being centered. I routinely use the rules inscribed on the router lift plate to adjust the fence to exactly what I want for distance on rabbetts and dadoes. I think I would notice 40 thou.

As a matter of fact, the router lift came with a 1/2” pointed rod to mount in the router collet to assure centering. I used it when I first setup the router. I can’t say it is within .001 inch (this is woodworking after all) but I know for sure it is less than 1/16” (~30 thou)! I used a machinist’s ruler and the smallest insert and measured down to 1/64”. But the point on the rod was almost 1/64”. I may try jbmaine’s technique with a dial indicator just to see how close it really is.

As I said, it is an old Woodpecker lift, used a machined aluminum spacer, machined aluminum inserts (they may have gone plastic by now too) and A deWalt 616 router – it was dead-on from the factory with no fuss about moving the router around.

-- "Find out what you cannot do and then go do it!"

View LD100's profile

LD100

9 posts in 201 days


#18 posted 01-11-2021 10:43 PM

Thanks EEngineer. I agree it’s a must to have the bit centered on the insert for certain operations.

I looked for images of the Woodpecker 420 router lift online. It appears to have a centering router clamp. That is, there are elements (it looks like three at 120 deg intervals) that come in from the outside to clamp the router, naturally centering it. The SawStop’s clamp only tightens down on one side, which can shift the router over.

I like the 420’s clamp design better than the SawStop lift’s clamp. As I mentioned above, I really like the SawStop’s lift mechanism, but not so much its router clamp mechanism. But, I did finally get it centered and my intention is to leave it locked in place.

View EEngineer's profile

EEngineer

1137 posts in 4699 days


#19 posted 01-12-2021 05:49 AM

”But, I did finally get it centered and my intention is to leave it locked in place.”

Yeah. I bought the DW616 specifically for the router table. I kept the base thinking I would dismount the router and use it for manual routing. 13+ years now and the router has never been out of the router table. I find there just aren’t many things I cannot do on the router table. For those things I do need to do by hand (laminate trimming on big panels comes to mind) I have an ancient Craftsman router that I use.

-- "Find out what you cannot do and then go do it!"

View HokieKen's profile

HokieKen

17548 posts in 2224 days


#20 posted 01-12-2021 11:49 AM



...
But, I did finally get it centered and my intention is to leave it locked in place.

- LD100

I hope that works out for you but I decided pretty quickly that the 690 was underpowered after I built my table. It will depend on what kinds of projects you do though. YMMV…

-- I collect hobbies. There is no sense in limiting yourself (Don W) - - - - - - - - Kenny in SW VA

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